The rapid and accurate detection of extremely low concentrations of antigens and antibodies in liquid samples has been recognized as a valuable tool in the diagnosis and treatment of disease and in substance detection for safety, law enforcement, therapy and environmental applications. The development of recombinant DNA and hybridoma techniques has vastly increased the number of antibodies, antigens and haptens which can be detected by immunologically specific reactions and has improved the sensitivity of these detection methods. Previous investigators have worked with competitive assays which utilize radiation (RIA) and fluorescence to qualitatively and quantitatively signal the presence of the analyte (i.e., the substance to be detected). These techniques require expensive reagents and elaborate instrument schemes to detect and measure a signal related to the presence and amount of the target analyte.
The monoclonal antibody sandwich assay technique has also evolved as a quick and accurate method to detect immunological analytes. In the widely used ELISA, an enzyme (rather than radioactive or fluorescent) tagged component has been used to form a tagged antibody sandwich, which upon addition to the enzyme substrate generates a visually detectable calorimetric signal. One drawback of the ELISA technique is that a relatively expensive reagent (enzyme-tagged immunological component) must be used to complete the sandwich.
One analyte detection technique which does not require tagged molecules in order to generate a measurable signal related to the presence and amount of analyte present involves the use of an ellipsometer to detect changes in refractive properties on a flat reflecting surface. These surface refractive property changes occur when a liquid phase antibody/antigen binds to a solid phase antigen/antibody preadsorbed on the flat reflecting surface. The drawback of this technique, (Rothen, A., Helv. Chim. Acta, 33 834 (1950)), is that the ellipsometer is a complex and expensive instrument, making the use of this technique costly.
BioStar (Colorado) has recently developed an "interference slide" technology for detecting immunological analytes in liquid samples. This technique utilizes visual properties of interference, and anti-reflective coatings, to create altered light responses for thickness changes indicative of the target analyte.
The present invention provides an optical immunosensor which is more sensitive than the BioStar device, and which can be used to measure the amount of analyte present in a liquid sample qualitatively, semi-quantitatively, or quantitatively.
It is therefore one object of the present invention to provide films and substrates which are selected to yield distinctly different colors under assay conditions.
It is another object of the present invention to provide an optical immunosensor device fabrication method which is easy and inexpensive.
It is a further object of this invention to provide an optical immunosensor device which can be used to make qualitative, semi-quantitative and quantitative determinations of the analyte present, based upon the color changes resulting from thickness changes and upon comparisons of these colors to known standards.
These and further objects of the present invention will become apparent to the ordinary artisan by reference to the following specifications and drawings.